1. Field of the Invention
The present invention relates to a contact module, a connector, and a method of producing the contact module.
2. Description of the Related Art
Connectors are classified into various types, according to the shape, the purpose of use, the connecting method, and other factors.
For instance, according to the mounting type, connectors can be classified as LSI sockets that are connected to LSIs, wiring board connectors that are connected to wiring boards, and relay connectors that are used for connecting cables to cables.
Among the above connectors of various types, the wiring board connectors can be further classified into edge-card connectors and two-piece connectors.
FIGS. 1 and 2 show conventional edge-card connectors, each of which is used to connect a mother board 1 and a daughter card 2. A pad 3 provided in the pattern (not shown) formed on each side of the daughter card 2 is interposed between the daughter card 2 and a contact 4. Here, the patterns on the daughter card 2 are used as the inserting ends. A connector 5a shown in FIG. 1 is a through-hole mounting type. More specifically, one end of each of the contacts 4 is inserted into a through hole (not shown) formed through the mother board 1, and is then soldered and fixed thereto, so that the connector 5a is mounted to the mother board 1. On the other hand, a connector 5b shown in FIG. 2 is a surface mounting type. More specifically, one end of each contact 4 is soldered and fixed to a pad 6 formed on the mother board 1, so that the connector 5b is mounted to the mother board 1.
FIG. 3 shows a two-piece connector 5c. In FIG. 3, a receiving connector 5c-1 is mounted to a wiring board 7, while an inserting connector 5c-2 is mounted to a wiring board 1. The two connectors 5c-1 and 5c-2 are engaged with each other, so as to form the two-piece connector 5c. 
Although the connectors differ in shape according to the type of mounting as described above, the wiring board connectors, the LSI sockets, and the relay connectors each have a number of pin-shaped or tongue-shaped contacts that are made of a metal material and are accommodated in a housing (denoted by reference numeral 8 in FIGS. 1 through 3) made of an insulating resin.
If the contacts are of press-fit types, having pin-like shapes, a flat metal material is formed into a plurality of contacts by a cut-out technique, a stamp-out pressing technique, bend pressing technique, or a mold pressing technique. If the contacts have tongue-like shapes, a flat metal material is also formed into a number of contacts by a cut-out technique or a stamp-out pressing technique.
A connector is required to have certain mechanical characteristics, as well as electric characteristics that will be described later.
When a connector is fitted to a substrate or the like, it is desirable that the connector can be inserted into the connecting opening of the substrate with only low insertion force. Also, after the insertion, it is essential for the contacts to be in sure contact with the electrodes of the substrate. In view of this, a so-called LIF (Low Insertion Force) structure in which the contacts have spring-like characteristics should be employed, so as to obtain great contact force after the contacts are inserted with low insertion force. Meanwhile, when the contacts are inserted, it is not desirable to cause abrasion and wear due to the sliding contact between the contacts and the electrodes. In view of this, a so-called ZIF (Zero Insertion Force) structure, in which the electrodes are brought into contact with the contacts only after the connection is completed, should be employed so as to prevent the sliding contact between the contacts and the electrodes. Also, to prevent the above problems, various types of contacts have been developed in terms of shapes, materials, and surface-finishing methods.
Other than the above characteristics, a connector is always required to have low noise by reducing the size, increasing the contact density, increasing the speed (or the transmission speed), and restricting crosstalk.
However, a conventional connector has pin-like contacts as described above. Because of this, there is naturally a limit to the size of the connector and the contact density. As for the contact density, for instance, it is difficult to arrange the contacts at intervals narrower than 0.2 or 0.3 mm.
Having a three-dimensional structure as described above, a conventional connector is designed and manufactured by using a simulation and three-dimensional CAD or CAE in such a manner that the electric characteristics satisfy predetermined conditions. Because of the complicated three-dimensional shape, it is difficult of maintain the variation of the impedance level within ±10%. This leads to difficulties in eliminating noise due to non-matched impedance.